software mode uses extra rendering threads to speed up emulation and it works great for me but i was wondering could there ever be HW extra rendering threads to speed up hardware mode even more for some people that have great gpus but dont get up to crack speed and speed hacks ruin emulation for alot of games so i was wondering would HW ERT be doable?

Software Mode uses extra Rendering Thread of the CPU to render. The GPU is not used in the process of rendering.
I don't think GPU have something so-called threads. It has a Processor and shaders with raster operators.
More Multi-Threading is possible with CUDA but pcsx2 hates parallel threads which CUDA uses.

Software Thread makes faster for you because you probably have a quad-core PC or high with 4 to 8 threads free.

Hardware rendering uses a different concept of rendering. It cannot use more CPU cores and it wouldn't make much difference to begin with.
There's a bit of multithreading going on in D3D and the whole plugin runs on the MTGS thread, so yea, we're doing the best we can already